抗偏移行攻击盲鲁棒图像水印算法

利用区域点设计抗偏移行攻击修正方法估算偏移行数,把偏移行攻击转化成剪切攻击,从而提出一种抗偏移行攻击盲鲁棒图像水印算法。嵌入端将原始图像分割成互不重叠的子块,通过调整每个子块四列像素数值大小嵌入水印。检测端先对攻击后的含水印图像进行抗偏移行攻击修正,然后通过像素值大小比较和多数判决原则提取水印。算法具有良好的不可见性,而且实现了盲提取。算法采用抗偏移行攻击修正,在抵抗偏移行攻击上表现出较强的鲁棒性。实验结果还表明,算法在抵抗高斯低通滤波、剪切、添加椒盐噪声、添加高斯噪声常规信号处理上也表现出较强的鲁棒性。

自走式甜菜联合收获机自动对行检测装置的设计

甜菜是甘蔗以外主要糖来源之一,在生产生活过程中具有重要地位。为提高甜菜的收获效率,需要研发收获机自动对行控制系统和控制技术,而对行检测是实现甜菜自动对行收获的基础与难点。为此,设计研发了一种适用于自走式甜菜收获机的对行检测装置,并进行了性能测试。实验结果表明:所设计的装置能够精确检测偏离作物行的程度,为实现自走式甜菜联合收获机的自动对行控制奠定了基础。

基于Flush+Reload的DES算法Cache计时攻击

在数据加密标准(DES)算法上使用Flush+Reload方法的Cache计时攻击,存在难以确定S盒元素行偏移位的问题。为此,利用S盒在Cache中会发生不对齐分布的特征,提出一种偏移位确定方法。采用clflush指令刷新Cache地址行,以驱逐Cache中DES算法的S盒信息,确定S盒元素的位置信息。利用密码算法在查询S盒时泄露的Cache计时信息获取明文与密钥异或后的中间态值,并通过该值和已知明文的相关性恢复密钥。实验结果表明,该方法能够有效确定S盒元素的行偏移位,提高针对DES算法Cache计时攻击的效率。

农业机器人视觉导航路径识别方法研究

针对农业机器人视觉路径识别的识别率低、速度慢以及易受光照、杂草影响的问题,提出基于混合阈值与偏移行中线的视觉导航路径识别方法。采用光照无关量进行光照干扰的剔除,利用混合阈值方法分割图像,给出基于偏移行中线的方法划分作物行。实验结果表明,与传统农业机器人作物行识别方法相比,该方法数据运算量小,平均耗时200 ms左右,作物行识别准确率达98%,能够有效地确定农业机器人的导航路径。

Getting pre-stack time migration travel times from the single square root operator

Improving the focusing capability of pre-stack time migration allows the imaged section to reflect structural characteristics, depth, and interface shape and it is a key step for the preparation of the initial depth migration velocity model. The traditional symmetrical travel time equation is derived based on the assumption of a layered model. It is difficult to achieve the desired effect of focusing in media with strong lateral variation. The nonsymmetrical travel time equation based on Lie algebra and a pseudo-differential operator contains a lateral velocity derivative which can improve the focusing capability even in strongly lateral variable media and also the computation precision of the weight coefficients for relative amplitude preservation. Compared with the symmetrical methods, the nonsymmetrical method is more effective. In this paper, we describe several key steps of nonsymmetric pre-stack travel time calculation and present some test results using synthetic and real data.

Dynamic stability of quadruped robot walking on slope with trot gait

The dynamic stability of a quadruped robot trotting on slope was analyzed.Compared with crawl gait,trot gait can improve walking speed of quadruped robots.When a quadruped robot trots,each leg is in the alternate state of swing phase or supporting phase,and two legs in the diagonal line are in the same phase.The feet in the supporting phase form a supporting region on the ground.When a quadruped robot walks on slope,the vertical distance from zero moment point(ZMP) to the supporting diagonal line is defined as ZMP offset distance.Whether this distance is less than the maximum offset distance or not,the stability of robot trotting on slope can be judged.The foot trajectory was planned with the sinusoidal function.Based on the kinematic analysis,the ZMP offset distance of quadruped robot under different slope angles,step length and step height was calculated,then the reasonable slope angle,step length and step height for quadruped robot trotting on slope to keep dynamic stability can be determined.On the other hand,the posture angle of quadruped robot should be controlled within the desired range.Computer simulations were executed to verify the theoretical analysis.The study will provide reference for determining reasonable step parameters of the quadruped robot.

维修集锦

DVD 设置错误造成的故障以下故障现象都因设置错误造成的,维修人员维修时应特别留意,首先要确认是影碟机的性能问题还是设置问题。维修前可调试相关的功能是否设置妥当。机型:TCL TD-F3710P/3720P 逐行扫描 DVD 机。故障现象:无视频或视频信号输出且不同步(呈黑屏)。分析检修:检查发现"视频输出"功能未设置好。

A Critical Analysis of Methodologies Evaluating Biodiversity in Offset Banking

The assessment of ecological impacts represents a key element of biodiversity offsetting success. After briefly introducing the main controversies arisen on biodiversity monetization and defining biodiversity banking schemes, discussions will be focused on evaluation methods mobilized in the context ofbiodiversity offset banking. Although there is currently no fixed framework assessing environment due resolutely to the specific nature of biodiversity, evaluation methods are analyzed through a review of the academic and empirical literature. This step allows to select few methods justifying these choices and presenting their pros and cons by keeping the aim to contribute to the debates. Thus, ecological assessments （service-to-service and resource-to-resource） and economic valuations （value-to-value and value-to-cost） carried out in biodiversity banking schemes will be distinguished. Finally, this paper will emphasize the inherent differences of the two evaluating forms and their specificities on the one hand, and highlight their opportunities and risks from methodological perspective on the other hand.

Computation of the Viscous Hydrodynamic Forces on a KVLCC2 Model Moving Obliquely in Shallow Water

The viscous hydrodynamic force and moment on ships moving obliquely in shallow water are important for ship navigation safety.In the paper,the viscous flow field around a KVLCC2 model moving obliquely in shallow water is simulated and the hydrodynamic drag,lateral force and yaw moment acting on the hull are obtained by a general purpose computational fluid dynamics(CFD) package FLUENT with shear-stress transport(SST) k—ωturbulence model.The numerical computation is performed at different drift angels and water depths.The numerical results are compared with experimental results,and a good agreement is demonstrated.